Preparation of sulphur-containing diesel fuel ignition agents



June 18, 1940. c. H. sr-:ELEY Er A1.

PREPARATION '0F SULPHUR-CONTAINING DIESEL FUEL IGNITION AGENTS FiledJune 30, 1937 3 Sheets-Sheet 1 mwN Clarence E Seeley a 'HArvesonATTORNEY June 18. 1940. c. H. SEI-:LEY Er AL 2,205,126

PREPARATION F SULPHUR-CONTAINING DIESEL FUEL IGNITION AGENTS Filed June30, 1937 3 Sheets-Sheet 2 5L-y 2 .afm/N 1:92 ron/52 53 CO/l.

HB4 TER WASH/IVG J6 TOWERS SEI? DOCTOR SETTLR J n ven i'orzs L'larenel.See/ey I MauriceIA/fvasan @MM/( A'ITCRNEY c. H. sEELEY r-:r A1.2,205,126

Filed June 30, 1937 3 Sheets-Sheet 3 WeHAn/esm .xokooh *SSW f n venrols(J/arenceH. See/gy ATTORN EY wn zh www NNN H mwN June 18, 1940.

ranrAnArIoN oF sULraUa-coNIAINING DIESEL FUEL IGNITION AGENTS Patented'June 18, 1940 UNITED STATES PATENT OFFICE PREPARATION FSULPHUR-CONTAINING DIESEL FUEL IGNITION AGENTS Application June 30,1937, Serial No. 151,166

Claims.

This invention relates to the preparation of sulphur-containing Dieselfuel ignition agents. The invention relates more particularly to themanufacture of such agents from light petroleum dis- 5 tillatescontaining substantial quantities of mercaptans.

Most commercially available Diesel fuel oils, especially those made fromnaphthenic type crude oils or containing considerable quantities ofcracked stocks, have ignition characteristics which make them poorlyadapted for use in certain types of Diesel engines, particularly thoseof the high speed type. These engines require 1 3 fuels which have ashort delay period between injection into the cylinder and ignition ofthe oil. It has been proposed to add small quantities of variousmaterials to Diesel fuels to reduce the delay period and accelerateignition in the engine, but these proposed ignition accelerators are 20generally rather expensive pure organic compounds.

One object of this invention is to provide a method of preparingsulphur-containing Diesel fuel ignition agents which are inexpensive and25 yet very effective in accelerating ignition of the fuel. Anotherobject is to prepare these ignition agents from light petroleumdistillates containing substantial quantities of mercaptans. Stillanother object is to provide a process for ob- `3q tainingsulphur-containing Diesel fuel ignition X agents in concentrated formfrom petroleum distillate. Further objects will be apparent from thefollowing detailed description read in conjunction with the accompanyingdrawings, in

35 which:

Figure 1 shows diagrammatically one form of apparatus suitable forcarry-ing out the invention;

Figure 2 shows diagrammatically an apparatus 40 suitable for practicinga modication of the invention including the step of rerunning thepetroleum distillate after washing with alkali; and

Figure 3 shows diagrammatically a form of apparatus for carrying out thestep of sulphurizing 45 the recovered sulphur compounds.

In carrying out the invention a petroleum fraction containingsubstantial quantities of mercaptans is treated with an aqueous solutionof a caustic alkali such as sodium or 50 potassium hydroxide, the spentcaustic solution containing mercaptides is treated with a revivifyingagent, such as air, oxygen, or steam, to revivify the same and torecover the sulphur compounds therefrom, the sulphur compounds 55 aredissolved in a petroleum distillate such as Diesel fuel oil, and theresulting solution is sulphurized with a sulphurizing agent such assulphur or an alkali polysulphide solution to produce a concentratedsolution of the ignition agent in Diesel fuel oil. In a modification ofthe process the distillate after alkali treating is rerun and theunvaporized residue, which contains sulphur compounds not removed by thealkali solution, is added prior to the sulphurizing stage to thesolution of sulphur compounds obtained in the revivication of the spentcaustic solution.

By means of this invention a highly effective sulphur-containing Dieselfuel ignition agent is prepared at low cost from materials available inthe refinery, and at the same time a petroleum fraction containingsubstantial quantities of mercaptans is eiciently refined Whilemaintaining a low consumption of caustic alkali solution.

Referring now to Figure 1, a sour petroleum distillate containingsubstantial quantities of mercaptans is introduced by suitable means(not shown) through line I0 into the bottom of treating tower II. Thisdistillate, which preferably contains at least 0.1% of mercaptansulphur, may be obtained from any source, such as the cracking ordistillation ofhigh sulphur crude oils or fractions thereof, but aparticularly suitable distillate is the polymer produced by thecatalytic polymerization of gases containing large amounts of hydrogensulphide, for example 200 or more grains HzS per 100 cu. ft. Such gasesmay be formed in the cracking of oils high in sulphur. Suitablepolymerization catalysts are phosphoric acid on kieselguhr or sodiumaluminum chloride. The sour distillate is treated countercurrently intower II with an aqueous solution of an alkali, such as an aqueouscaustic soda solution containing for example -35% NaOH, which isintroduced into the upper portion of tower II by means of line I2. Thecaustic solution reacts with the mercaptans in the distillate to formalkali mercaptides, which' are preferentially soluble in the causticsolution. The treated distillate is removed from the tower through lineI3, and may be further treated by well known means, e. g., sweeteningwith doctor solution, to produce finished motor fuel.

The spent caustic solution containing mercaptides is removed from thebottom of tower II through line I4 and mixed with oxygen, air, oroxygen-containing gas from a suitable source, which is illustrated inthe drawings by oxygen tank I5, supplied through line I6. The mixture ofspent caustic solution and oxygen or air is then passed through reactioncoil I1, which may if desired be heated with steam or other suitablemeans, and introduced through line Il into tire top of washing tower i9.The oxygen or air introduced into the spent caustic reacts with themercaptides to form disulphides and other sulphur compounds, andregenerates the caustic solution. A petroleum distillate such as Dieselfuel, is introduced into the bottom of tower il through line 23, andnows up the tower countercurrent to the caustic solution therein. Thedisulphides and other sulphur compounds, which are preferentiallyoil-soluble, dissolve in the Diesel fuel, and the revivined causticsolution, now free from sulphur compounds, is Areturned from the bottomof tower i! to the top of tower Il by means of line 2|, pump 22, andline i2. The caustic solution in the circulating system may bemaintained in suillcient quantity and at the proper concentration byadding fresh caustic solution from a suitable source (not shown) atintervals through pump 23 and line 24.

The Diesel fuel which now contains a large quantity of dissolved sulphurcompounds, is removed from the top of tower I9 through line 25, passedthrough cooler 26 into separator 21, in which excess oxygen or othergases are separated from the Diesel fuel and removed through vent 23.The air and/or gas-freed Diesel fuel is removed from the bottom ofseparator 21 by means of line 28 and pump 30 and mixed with a stream ofa sulphurizing agent'from line 3| in line 32 and mixer 33. Thesulphurizing agent for example m'ay be elementary sulphur, aconcentrated solution of sulphur in an organic solvent such as carbondisulphide, or a concentrated aqueous solution of an alkali polysulphidesuch as sodium, potassium, or ammonium polysulphide.

The mixture of sulphurizing agent and Diesel fuel containing sulphurcompounds is then passed through line 34 to reaction coil 35, which maybe heated by steam or other suitable means. In this coil a reactiontakes place between the sulphurizing agent and the sulfur compoundsdissolved in the Diesel fuel to produce a concentrated solution of asulphur-containing ignition agent in Diesel fuel. The finished productis Vwithdrawn from the system through line 36, and

may be blended in small quantities with Diesel fuels to improve theirignition characteristics. If desired the solution of ignition agent maybe further treated before addition to Diesel fuel. For example it may besweetened with doctor solution in the conventional manner, or treated byother reagents, such as weak alkali polysulphide solution, to remove anyexcess of free sulphur which may remain.

When concentrated alkali polysulphide solution is used as sulphurizingagent, the solution of ignition agent is separated from the spentpolysulphide solution in a suitable separator not shown, and the lattersolution may be returned to line 3| after it has been brought up tostrength by the solution of sulphur therein.

The invention may be carried out using various types of apparatus, andhas many modifications, one of which is illustrated by Figure 2.Although the sour distillate to be treated may be any of thosepreviously described, this modification of the invention will bedescribed using, as the distillate to be treated, the crude polymer fromthe catalytic polymerization of unsaturated gases containing hydrogensulphide. This polymer preferably contains at least 0.3%

sulphur of which (i5-90% is sulphur in the form of mercaptans.

Crude polymer is withdrawn from tank 4l by means of line 4i and pump 42,and introduced into line 43, and mixed therein with an aqueous alkalisolution, for example a 20%' solution of caustic soda obtained from asource hereinafter described. Themixture of polymer and caustic solutionis passed through mixer 44 and contact coil 4I, in which the causticsolution extracts `a major portion of the mercaptans from the polymer asmercaptides. The mixtures then introduced into caustic settler 4i, inwhich the treated polymer and the now spent caustic are allowed toseparate into two layers. 'Ihe Upper polymer layer in settler 40 isremoved through line 41, heated in a conventional pipe heater 4l andpassed into rerun tower 49, which is provided with a reboiler orstripping means 5I and a reflux line Il. The tower bottoms (unvaporizedresidue) which contains high-boiling sulphur compounds, is removedthrough line l2, or it may be utilized in the process in a mannerhereinafter described.

The overhead from rerun tower 43, which is a relatively low-sulphurpolymer fraction of the desired boiling range, hereinafter referred toas polymer gasoline, is withdrawn through line 53, condensed incondenser 54, and introduced into separator l5, from which uncondensiblegases, such as hydrogen sulphide formed by decomposition of sulphurcompounds during the rerunning step, are removed through went 56. I'hepolymer gasoline is withdrawn from separator 55 by means of line 51 andpump 53. A portion of this gasoline is passed through line 53 andcombined with a stream of fresh doctor solution introduced into thesystem by means of a line and a pump 6|. 'Another portion of the polymergasoline withdrawn from separator 55 by means of line 51 and pump 53 ispassed through line 5| as reux for rerun tower 49, as hereinbeforedescribed.

The mixture of polymer gasoline and doctor solution is passed throughmixer 62 and contact )coil 63 to doctor settler 64, where the finishedpolymer gasoline and the spent doctor solution are allowed to separateinto layers. The finished polymer gasoline is withdrawn through line 65to storage, and the spent doctor solution is removed through line 66. Bymeans of this doctor sweetening step, any volatile mercaptans whichescaped removal in the caustic treating step, or which were formed bydecomposition of sulphur compounds during the rerunning step areconverted into unobjectionable forms, and the polymer gasoline isrendered suitable for sale.

The spent caustic from caustic settler 46 is removed by means of line81, pump 68 and line 33 and introduced into the upper portion of blowtank 10. In blow tank 1B, the spent caustic is contacted with eithersteam or air introduced through line 1i and a distributing device 12located in the bottom thereof. When steam alone is used to revivify thespent caustic the solution is maintained at a temperature favoringhydrolysis of the mercaptides therein, e. g., 215-235 F. and the steamis preferably superheated suiliciently to maintain the caustic at thistemperature without either increasing or decreasing the volume ofsolution. If desired a portion of the necessary heat may be supplied bymeans of heating coil 13.

t The steam hydrolyzes the mercaptides in the spent caustic to sodiumhydroxide and mercaptans, and the latter are volatilized and passoverhead together with steam through line 14 and condenser 15 intoseparator 16, from which uncondensible gases are removed through vent11. The condensed steam and recovered mercaptans separate into twolayers in separator 16, the lower layer comprising water containingdissolved mercaptans being removed by.

means of line 18 and pump 19, and introduced through line. 88 into theupper portion o1' washing tower 8|. Diesel fuel or similar petroleumdistillate is introduced into the bottom of washing tower 8| by means ofline 82, passes through the tower counter-current to the stream ofaqueous solution, and dissolves the mercaptans from the-Water, thusrendering the latter sufclently free from odor that it may be discardedto the sewer through line 83. 'Ihe solution of mercaptans in Diesel fuelis removed from washing tower 8| through line 84 and valve 85 into line86, valves 81 and 88 being closed.

'I'he regenerated caustic solution is removed from blow tank 18 throughline 89, valve 98 and line 9|, valves 92 and 93 being closed, and isreturned by means of pump 94 to line 43 for the treatment of a furtherquantity of crude polymer as hereinbefore described. From time 'to timefresh caustic solution of suitable concentration ls introduced into line43 by-means of line 95 -and pump 96 to maintain the concentration andquantity of caustic solution in the system. Y l

When the spent caustic in blow tank 69 is revivied by blowing with air,suiiicient steam is preferably mixed therewith to prevent undueconcentration of the solution. The caustic solution is maintained at atemperature of 195- 220 F. so that the mercaptides therein are oxi-v 16by means 0f vent 11. .Some water vapor isv carried overhead togetherwith the disulphides from blow tank 18 and condensed in condenser 15.This aqueous condensate separates as a lower'layer in separator 16, andis washed with Diesel fuel as hereinbefore described.

It is preferred in this case to wash the revivied caustic solution fromtank 18 with Diesel fuel in order to remove small amounts of sulphurcompounds therefrom. This step is desirable because disulphides are lessvolatile than the corresponding mercaptans and cannot be completelycarried overhead to separator 16, but is not essential because heavydisulphides contained in the reviviied caustic solution will dissolve inthe polymer being treated in the alkali washing stage and will beremoved therefrom in the tower bottoms in rerun tower 59.

When it is desired to remove the disulphides from the revivied causticsolution, valves 85 and 98 are closed, and valves 81, 88, 92 and 93 areopened. The revivied caustic solution then oWs from the bottom of blowtank 18 through line 89, valve 92, and line 91 intothe top of washingtower 98, in which it is countercurrently washed with Diesel fuel fromwashing tower 8| introduced into the bottom of washing tower 98 by meansof line 84, valve 81, and line 99. The caustic solution, nowsubstantially free of disulphides is recycled to the alkali treatingstage by means of line |88, valve 93, line 9| and pump 94. The Dieselfuel solution of disulphides and other sulphur compounds is removed fromthe top of washing tower 98 through line |8|, valve 88, and line 86.

The Diesel fuel solution of sulphur compounds in Iline 86 is thelinmixed with the sulphur compounds concentrated in the upper layer inseparator 16 by means of lines |82 and |83. The sulphur compoundspresent will be predominantly mercaptans or disulphides, depending onthe agent used to revivify the caustic., In either case,the towerbottoms from rerun tower 49, which is rich in sulphur compounds, may beadded to the solution by opening valve |84, and passing the bottomsthrough line |85 which joins line |83. The solution is then charged bymeans of pump |86 to the sulphurizing stage, which is similar to thatdescribed in connection with Figure 1. A sulphurizing .agent such assulphur, a concentrated solution of sulphur in an organic solvent or aconcentrated aqueous solution of alkali polysulphide is added to thesolution throughv able for addition to Diesel fuel in relatively smallamounts to improve the ignition characteristic thereof.

Another embodiment of the'invention comprises broadly the process ofsulphurizing sulphur compounds such as mercaptans or disulphides at hightemperatures and pressures in solution in Diesel fuel or a similarpetroleum fraction by means ofa concentrated solution of alkalipolysulphide, washing the productV with Weak polysulphide solution, andsweetening with doctor solution.

One method of carrying out this embodiment of the invention isillustrated by the flow diagram shown in Figure 3. A solution of sulphurcompounds in Diesel fuel, such as the unsulphurized product obtained bythe process illustrated by Figure 2 when using steam for blowingthespent caustic, is introduced into the system by means of pump |28 andline |2| and passed through heater |22. This solution may containprincipally disulphides, but preferably contains 5-20% of mercaptans. Itis supplied to the heater at elevated pressure, e. g., -1008 pounds persq. in. and is heated therein to an elevated temperature such as Z50-408F. The heated solution is then passed upward through treating towers|23, |24, |25, and |26 successively by means of lines |21, |28', |29,and |38. A concentrated aqueous solution of an alkali polysulphide suchas NazSx obtained from a source hereinafter described is forced by meansof pump |3| and line |32 through heater |33 in which it is heated to anelevated temperature, and then passes successively down treating towers|26, |25, |24, and |23 by means of lines |34, |35, |36, and |31. It willthus be seen that the solution of sulphur compounds in Diesel fuel issubjected to countercurrent contacting with increasing concentrations ofpolysulphide solution at elevated temperatures and pressures, thussulphurizing the dissolved sulphur compounds to produce compounds havingignition accelerating characteristics. Although four treating stages areshown, more or fewer stages may be used. If desired crude sulphurcompounds such as mercaptans from any suitable source may be introducedinto the second treating stage of the system by means of pump |38 andline |39 connected to line |28, through valve |48, which at other timesis normally closed.

'I'he sulphurized solution is withdrawn from the top of tower |28through line Mi and passed through cooler |42 and up through treatingtowers |43 and I in sexies by means of lines III and |46.' Thepolysulphide solution is removed from the bottom of tower |23 by meansof line |41, cooled in cooler I, and circulated down towers i and I inseries by means of pump i, and lines Il. and ill. It will thus be seenthat the solution of sulphurized compounds in Diesel fuel, which nowcontains free sulphur due to decomposition of the polysulphide solutionat an elevated temperature, is countercurrently washed with apolysulphide solution which is relatively weak, i. e., low in sulphur,which dissolves free sulphur from the oil solution. The weakpolysulphide solution from the bottom of tower I is introduced by meansof line il! into a sulphur dissolving drum |53, in which its sulphurcontent is brought up to the required strength, and the resulting strongsolution is withdrawn by pump ISI through line i andrecirculated throughthe system. The supply of sulphur in drum III is replenished from timeto time by the addition of sulphur through hopper lila. Additionalalkali sulphide or polysulphide solution may also be introduced intodrum III by suitable means (not shown) in order to maintain thenecessary volume of polysulphide solution in the system.

The solution of sulphurized compounds in Diesel fuel is withdrawn fromthe top of tower i by means of line Ill and introduced into the bottomof sweetening tower |58 in which it is treated with doctor solutionsupplied from a suitable source by means of line |51. The spent doctoris withdrawn through line |58. The nal product, which is removed throughline I", is a sweet concentrated solution of Diesel fuel ignition agentin Diesel fuel.

While certain specific embodiments o! the invention have been describedin detail, we do not limit `4ourselves thereto except as defined by thefollowing claims which should be construed as broadly as the prior artwill permit.

We claim:

1. The process of preparing a solution consisting mostly of alkylpolysulphides dissolved in a hydrocarbon solvent, said solution beingadapted for use as a Diesel fuel ignition agent, comprising dissolvingan aliphatic sulphur compound having not more than two sulphur atoms permolecule in said hydrocarbon solvent, sulphurizing the resultingsolution at an elevated temperature and pressure in the presence o f aconcentrated aqueous solution o! an alkali polysulphide, and washing thesulphurized solution with a relatively weak aqueous solution of analkali polysulphide.

2. The process of claim l wherein said aliphatic sulphur compound is analiphatic mercaptan.

3. The process of claim 1 wherein said allphaic sulphur compound is analiphatic disulphl e.

4. The process o1' claim l wherein said'elevated temperature is in therange from `about 250 l". to about 400 F. and 'said elevated pressure isin the range from about 100'to about 1000 pounds per square inch.

5. 'I'he process of preparing a solution consisting mostly of alkylpolysulphides dissolved in a hydrocarbon solvent. said solution beingadapted for use as s Diesel fuel ignition agent, comprising dissolving.an aliphatic sulphur compound having not more than two sulphur atomsper molecule in said hydrocarbon solvent. countercurrently treating theresulting solution with a concentrated aqueous solution of an alkalipolysulphide at an elevated temperature and pressure in a sulphurizingzone, removing the sulphurized solution from said sulphurizing zone,removing weak alkali polysulphide solution from said sulphurizing zone,washing said sulphurized solution with said weak alkali polysulphidesolution, removing sulphurized solution and weak alkali polysulphidesolution from said washing zone, dissolving sulphur in saidlast-mentioned polysulphide solution to increase the sulphur contentthereof, and recycling the sulphur-enriched alkali polysulphide solutionto said sulphurizing zone.

CLARENCE H. SEELEY. MAURICE H. ARVEBON.

